Convective-Air butane powered portable vaporizer

ABSTRACT

Vaporizer for extracting active compounds from a sample of plant material contained within the device, said vaporizer including a heat exchanger, said heat exchanger being shaped to provide for generation of significant heat to warm the air passing through the heat exchanger and into the mouthpiece connecting with the heat exchanger, the heat exchanger being located within a heat shield, the heat shield surrounds the chimney, the chimney being arranged above a butane lighter which when operated generates sufficient and controlled flame for impingement upon a segment of the heat exchanger to allow its air therein to be significantly heated for inhaling through the plant material contained within the mouthpiece to allow the user to extract the heated active compounds from the plant material for therapeutic and other inhalation.

CROSS REFERENCE TO RELATED APPLICATION

This non-provisional patent application claims priority to the provisional patent application having Ser. No. 61/634,579, filed on Mar. 2, 2012.

FIELD OF THE INVENTION

The concept of this invention is to provide butane fuelled portable vaporizer where hot air is drawn across and through a sample of plant material for providing therapeutic inhalation of its extracted and active compounds.

BACKGROUND OF THE INVENTION

A vaporizer is a device which is designed to extract the active compounds from a sample of plant material for therapeutic inhalation. The type of plant material can vary greatly—examples include (but are not limited to) mint, eucalyptus, lavender, and tobacco.

The vaporization process may seem very similar to smoking, but vaporization is preferable for several reasons. The plant matter is gently heated to a temperature just below combustion. This allows the active compounds in the plant matter to be volatilized (re: boiled off). The majority of active compounds will vaporize between 220 deg. F. and 420 deg. F. Because high temperatures are avoided, combustion is avoided. No combustion=no pyrolysis. Because pyrolysis is avoided, many carcinogens are never created. Although smoking is a very efficient and fast method of delivery to the body, it also has some very obvious drawbacks. Because the user ingests so many carcinogens while smoking, many people avoid therapeutic treatment with plant materials. With vaporization, many of drawbacks inherently tied to smoking are eliminated. This makes inhalation of plant materials for therapeutic effect a viable option for the health minded.

The process of vaporization also makes very efficient use of material. The combustion reaction (during smoking) generates too much heat. The excess heat actually destroys many of the active compounds before they can be ingested by the user. The process of smoking can be wasteful because a larger amount of material must be smoked to receive the same therapeutic benefit. The gentle heat of vaporization rises slowly enough to boil-off all of the active compounds. Because no active compounds are destroyed by high heat, a smaller amount of material is needed to deliver the same therapeutic effect.

Electrically/battery powered devices are shown in U.S. Pat. No. 6,990,978; U.S. Pat. No. 5,993,748; U.S. Pat. No. 4,141,369; U.S. Pat. No. 4,303,083. The most advanced of these devices is capable of adjusting heat output to ensure that the material to be vaporized stays within the desired temperature range. The length of the electrical vaporization devices are not portable and require electrical line power. Some electrical vaporizers are powered by batteries. While this does make the device portable by freeing it from line power, short battery life and lengthy recharge times are significant limitations. The device is not portable while the batteries are recharging, because it takes several hours to fully recharge the battery.

U.S. Pat. No. 6,717,494 describes a vaporizer attachment for a pipe so that the pipe can be coupled to an electric heat gun. While this is a very effective method of vaporization, the required tools and attachments make the process very cumbersome. The size of the system does not lend itself to portability. Also, the system is reliant on electrical line power, and therefore cannot be used at any location, and is not portable. The heat output of this system is easily controlled and adjusted with the heat thermostat.

As previously stated, select patents identify related structure pertaining to vaporization methods. For example, the U.S. Pat. No. 6,990,978 shows a Method and System for Vaporization of a Substance. This device does release the active constituents for inhalation without the reaction of harmful byproducts, as can be understood. But, the structure of the shown device is totally distinct and different from that of the current invention.

U.S. Pat. No. 5,993,748, to Wheeler, discloses a Hot Gas Extraction Device for Volatizing at least One Substituent of a Material. This device utilize hot air or gas for volatizing a material, but utilizes a non-flame type heating unit for heating a gas, and then causing the gas to pass through holes in its cap apparently for extraction purposes.

The patent to Burruss, U.S. Pat. No. 4,141,369, shows another Noncombustion System for the Utilization of Tobacco and Other Smoking Materials. This particular device is designed for smoking of tobacco, as can be reviewed from its description.

Another patent to Burruss, Jr., U.S. Pat. No. 4,303,083, shows a device in the shape of a pipe that provides for evaporation and inhalation of volatile compounds and medications. This device provides for the rapid evaporation of compounds and mixtures of such compounds that can achieve a vapor pressure at least one atmosphere, at temperatures of less that 250° C.

SUMMARY OF THE INVENTION

The concept of this invention is to provide a portable vaporization tool, and its system of usage, generally incorporating the convective-air butane powered portable (pocket) vaporizer, and its application and usage.

The device is designed to extract the active compounds from a sample of plant material for therapeutic inhalation, and is small enough to be easily portable. The design uses butane fuel (instead of electricity) to drive the process, which further enhances portability. The extraction is accomplished through the process of convection, wherein hot air is drawn across and through a sample of plant material.

The device consists of a small metal heat exchanger and a delivery tube which doubles as a sample holder and mouthpiece. The heat exchanger is heated externally by a butane/air flame. A small sample of plant material is placed into the end of the delivery tube. The heat exchanger and glass tube are brought together (a tapered fitting makes a tight fit between the two parts). As the user inhales, air is drawn through the heat exchanger, across the sample, through the glass tube and into the user's lungs. As the air travels this path, it heats up to approximately 400 degrees F. (in the heat exchanger). This hot air allows for a large amount of surface area contact between the plant material and the hot air. The hot air causes a phase change to the active compounds in the plant material. The compounds volatilize (boil) and turn from a liquid into a vapor. This vapor is inhaled by the user for therapeutic effect.

Generally, the vaporization system consists of two components, a heat exchanger and a mouthpiece. The heat exchanger is formed from a stamped piece of small diameter stainless steel tubing. The mouthpiece is formed from small diameter borosilicate glass tubing, where the inner diameter of the glass tube is equal to or smaller than the outer diameter of the stainless steel tubing.

The heat exchanger is a symmetrical design, and as such, can be used from either end. The two ends of the heat exchanger are round with a straight flat edge. Approximately one-third of the stainless steel tubing is flattened in the center of its length. This flattened section creates a constriction in the path of the airflow. The tubing is flattened so that the walls of the tubing become flat and parallel to each other. The flattened constriction increases the ratio of the metal to air, which focuses the energy into a smaller quantity of air. When the flame is applied to the outside of the heat exchanger, air passes through it and will rapidly increase in temperature. Thus, the walls need to be close enough to maximize air contact with the inner walls of the heat exchanger, but not so close that the airflow is restricted.

One end of the glass mouthpiece of this of this design is flared into a funnel shape to be slightly larger in diameter than the heat exchanger. The glass mouthpiece is shaped having a slight bulge, at its flared end of the mouthpiece. This bulge provides a location for a metal screen to snap into place. The screen creates a partition in the mouthpiece. The sample of material to be vaporized is placed into the flared end of the mouthpiece, and the sample will be confined to this chamber by the screen. The opposite end of the mouthpiece is rounded for comfort between the operator's lips.

When the heat exchanger and mouthpiece of this design are mated together, a continuous air path is created. When the operator presses these two components against each other, the taper of the glass flare seats tightly against the end of the heat exchanger. The operator now inhales on the rounded end of the glass mouthpiece. The air enters one end of the heat exchanger, passes through the glass mouthpiece and into the operator's mouth and lungs.

Material to be vaporized is arranged in very close proximity to the end of the heat exchanger.

In the usage of this invention, in order to maintain the proper temperatures for vaporization, the temperature of the system can be controlled in two ways. The first way is to vary the amount of heat being applied to the outside of the heat exchanger. The second way to control the temperature is to adjust the rate of the draw of the heated air. A rapid rate of inhalation passes more air through the system, and therefore, more air will remove heat at a faster rate from the heat exchanger. A slower rate of draw concentrates the same energy and results in a higher temperature airstream.

It is, therefore, the principal object of this invention to provide a device to extract the active compounds from a sample of plant material for therapeutic inhalation.

Another object of this invention is to provide a device that achieves a vaporization of the extracted active compounds for inhalation by the user.

Another object of this invention is to provide a portable vaporizer that is effectively coupled with a butane source of heat to achieve the extraction and vaporization of the active compounds from a plant material.

Another object of this invention is to provide a vaporizer device that is totally portable.

Still another object of this invention is to provide a butane powered vaporizer that is yet safe for usage and application.

Still another object of this invention is to provide a heat exchanger that is design formed to provide for constriction of the flow of air therethrough, which more effectively provides for a controlled heating of the air conveying the extracted ingredients from a sample of the plant material being inhaled.

These and other objects may become more apparent to those skilled in the art upon review of the summary of the invention as provided herein, and upon undertaking a study of the of the description of its preferred embodiment, in view of the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In referring to the drawings:

FIG. 1 provides a top view of the vaporizer system of this invention;

FIG. 2 shows a side view of the vaporizer system of this invention;

FIG. 3 shows the vaporizer system during its usage;

FIG. 4 provides a side view of the chimney means and the heat exchanger assembly when installed during usage;

FIG. 5 shows a top view of the heat exchanger and its chimney means;

FIG. 6 provides an exploded view of the vaporizer system of this invention, before its assembly into a compact portable unit for usage;

FIG. 7 provides a view of the assembled Convective-Air Butane Powered Portable Vaporizer of this invention; and

FIG. 8 shows a modification to the portable vaporizer of this invention, particularly with respect to the heat exchanger and mouthpiece for this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The vaporization system consists of two components—a heat exchanger and a mouthpiece. The heat exchanger is formed from a stamped piece of small diameter stainless steel tubing. The mouthpiece is formed of small diameter borosilicate glass tubing—where the inner diameter of the glass tube is equal to or slightly greater than the outer diameter of the stainless steel tubing.

In referring to FIGS. 1 and 2, the heat exchanger 1 is a symmetrical design and as such, can be used from either end. The two ends of the heat exchanger 1 a are round with a straight flat edge. Approximately ⅓ of the stainless steel tubing is flattened in the center of the length. This flattened section 1 b creates a constriction in the path of the airflow. The tubing is flattened so that the walls of the tubing become flat and parallel to each other. The flattened constriction increases the ratio of metal to air (the surface area stays the same while the volume is greatly diminished), which focuses the energy into a smaller quantity of air. When a flame is applied to the outside of the heat exchanger, air passing through will rapidly increase in temperature. The walls need to be close enough to maximize air contact with the inner walls of the heat exchanger, but not so close that the air flow is restricted (making inhalation difficult for the operator).

One end of the glass mouthpiece is flared 2 a into a funnel shape to be slightly larger in diameter than the heat exchanger. The glass mouthpiece is shaped with a slight bulge 2 b near the flared end of the mouthpiece. This bulge provides a location for a metal screen as at 2 c to snap into place. The screen creates a partition in the mouthpiece. A sample of material to be vaporized is placed into the flared end of the mouthpiece (vaporization chamber) and the sample will be confined to this chamber 2 d by the screen. The opposite end of the mouth piece 2 e is rounded for comfort between the operator's lips.

When the heat exchanger 1 and mouthpiece 2 are mated together, a continuous air path is created. When the operator presses these two components against each other, the taper of the glass flare 2 a seats tightly against the end of the hear exchanger 1 a (creating a seal that approaches air-tight). The operator now inhales on the rounded end of the glass mouthpiece. The air enters one end of the heat exchanger, passes through the glass mouthpiece and into the operator's mouth and lungs (i.e. all of the air will be forced to pass through the heat exchanger).

In referring to FIG. 3, the material to be vaporized (A) is in very close proximity to the end of the heat exchanger. A heat source (B) (e.g. butane, propane gas flame) is applied directly to the external walls of the flattened section of the heat exchanger. As the operator inhales, ambient air is drawn into the intake end (C) of the heat exchanger. The air increases in velocity as it is compressed into the flattened constriction (D). The tight constriction forces more air to come into direct contact with the hot stainless steel walls. The heat of the flame is transferred via conduction through the stainless steel walls of the heat exchanger 1 and into the air molecules. The relatively large surface area of the interior walls of the heat exchanger passes their entropy to the air molecules via conduction. The air slows as it decompresses into the larger output end of the heat exchanger. This hot, slow moving air now passes into the vaporization chamber (E) where the air molecules come into direct contact with the material to be vaporized (A). The hot air moves over and through the material to be vaporized. The process of convection transfers some of the heat energy from the hot air to the material to be vaporized. As the temperature rises in the vaporization chamber, the active compounds reach their boiling point, and begin to vaporize. When these compounds vaporize, they become part of the air stream and are carried into the operator's mouth (F). In order for vaporization to properly occur, a balance of temperature must be achieved . . . the temperature of the air in the vaporization chamber must be higher than the boiling point of the essential oils, but lower than the point of combustion. If the temperature rises too high, the material to be vaporized could possibly ignite. If the temperature is too low, the essential oils will never boil and will not be extracted.

In order to maintain the proper temperatures for vaporization, the temperature of the system can be controlled in two ways. The first way to control the temperature of the system is to vary the amount of heat being applied to the outside of the heat exchanger. A larger flame will output more BTUs and thus has more energy available to the system and a smaller flame will output fewer BTUs and impart less energy to the system. The second way to control the temperature of the system is for the operator to adjust the rate of draw (i.e. rate of inhale). As the operator inhales more quickly, more air passes through the system. With a constant size flame, more air will dilute the energy into more air molecules. More air will remove heat at a faster rate from the heat exchanger and will result in a lower temperature air stream. A slow rate of draw concentrates the same energy into less air molecules and results in a higher temperature air stream. A third method of heat control could be created by making the heat exchanger asymmetrical. If the flattened section was not centered between the ends of the heat exchanger, this would create a hot end and a cold end. The material to be vaporized would be closer or further from the flattened section of the heat exchanger depending on which end of the heat exchanger is mated with the glass mouthpiece.

A significant benefit of this system is the compact size. However, as long as the proper ratio of surface area to volume is maintained in the heat exchanger, this system can easily be scaled larger. A larger amount of material could be vaporized at one time using a heat exchanger with a diameter of 19 mm or greater.

The more preferred embodiment of the device incorporates both the simple heat exchanger and a butane/air lighter into a small handheld tool.

The mouthpiece 2 is formed from borosilicate glass tubing. It is 95 mm long×10 mm dia. It has an interior diameter of 8 mm (1 mm wall thickness). The end of the vaporization chamber is flared 2 a to a diameter of 12 mm so that it can mate tightly with the heat exchanger. A small bulge 2 b is formed 16 mm from the flared end. The bulge holds a 12.75 mm diameter screen 2 c which forms the mouth end of the vaporization chamber. The mouth end 2 e is flame polished.

The heat exchanger 1, which is fabricated from Type 304 Stainless Steel tubing, is 50 mm long and 8 mm in diameter. The tube has a wall thickness of 0.5 mm and an interior diameter of 7 mm. There is a constriction formed in the center of the tube 1 b, which measures 17 mm long and 12 mm wide. The constriction is formed by squashing the tube in a press until the walls are flat and parallel. The height of the constriction is 1 mm on the outside and 0.5 mm on the inside.

The heat exchanger is attached to torch-style butane lighter. This lighter premixes air with the butane to create an aggressive, blue flame that burns at 2200 degrees F. The lighter is composed of a butane fuel tank 5 with a refill valve 6 on the bottom. A clear acrylic plug 7 forms the top of the butane reservoir and doubles as a viewing window to gauge the fuel level. A piezoelectric igniter 8 slides into a pocket on the side of the fuel tank and is covered by a plastic button 11. Two plastic halves of the torch body housing 10 clamp onto the acrylic plug and keep the piezoelectric assembly in place. The torch body halves also contain the fuel adjustment valve 9, the venturi 12 and the torch head (which is composed of a brass flame orifice 13 and a ceramic enclosure 14).

The chimney 3 is machined from brass to form a hollow tube. It creates a combustion chamber which not only contains the flame, but also directs the hot exhaust gasses out of the top of the unit. It is designed to attach the heat exchanger to the lighter and hold it 16 mm above the flame orifice. This is an optimal distance for this device as it holds the heat exchanger in the hottest part of the flame.

The chimney is composed of two separate components (lower chimney and upper chimney). The lower chimney 3 is a brass tube 17 mm in diameter with a wall thickness of 1 mm. Four screws rigidly fix the chimney to the torch head. A saddle is cut into the top of this piece to support the heat exchanger at the proper height. The upper chimney 4 fits into the top of the lower chimney and clamps the heat exchanger in place. Two small screws lock these three pieces together.

Within the chimney, the interior diameter of the combustion chamber is 15 mm. The heat exchanger is 12 mm wide and is centered in the combustion chamber. This leaves a small semi-circular gap on either side of the heat exchanger 1. During operation, these negative spaces allow the flame and the hot exhaust gasses to flow up and around the heat exchanger. This structural arrangement keeps the inhaled air separate and uncontaminated by the flame and its exhaust.

A hole in the top center of the upper chimney contains a fine metal screen 16. This screen keeps debris from entering the chimney (which could potentially clog the semicircular exhaust path and/or clog the flame orifice). The screen also acts as a flame trap to prevent a flame from forming outside of the chimney.

The top of the tool is covered with a heat shield 17. During operation, the chimney and the heat exchanger become too hot to touch safely and thus require a heat shield to prevent accidental burns during normal use of the tool. The two plastic halves of the heat shield clamp onto the torch body housing and cover the torch head, chimney and heat exchanger. The assembled heat shield has one hole in the top center to allow the hot exhaust gasses to freely exit the top of the tool. There is also an opening on either side to allow access to both ends of the heat exchanger.

During use . . . the user depresses the igniter button, which activates the piezoelectric igniter and releases butane out of the fuel tank. The butane passes through a venturi which mixes air with the fuel and continues to the torch head. A spark from the piezoelectric igniter ignites the fuel air mixture. A blue flame forms at the torch head and passes into the bottom of the chimney and strikes the bottom of the heat exchanger. The flame and hot exhaust gasses pass up and around the heat exchanger through the semicircular gaps and out of the top of the chimney. After approximately twenty seconds, the temperature of the system will be great enough to vaporize. A sample of material to be vaporized is placed in the vaporization chamber, the mouthpiece is mated with either end of the heat exchanger and the operator draws in air to begin vaporization.

As can be seen in FIG. 7, the entire assembled vaporizer is disclosed, ready for usage. It shows how it may be assembled for single handed usage.

FIG. 8 shows the modified form of vaporizer, and particularly the interconnection between the heat exchanger and its mouthpiece. More specifically, in this configuration, a high temperature silicone rubber gasket G is placed over the end of the stainless steel heat exchanger 1, as noted. A retaining clip, such as a C clip H is placed behind the gasket to prevent movement of the gasket. The system can be used with or without the gasket, but the addition of the gasket includes several benefits. The glass mouthpiece is 2A and is flared into a funnel shape and is slightly larger or the same diameter than the outer diameter of the silicone gasket. The tight fit of the glass against the silicone gasket creates a truly air tight seal. A second benefit of this configuration is that the glass mouthpiece is flared much larger and allows for a much larger sample to be vaporized at one time. The most important benefit of this configuration is that the vaporization system can be used with one hand. There is a great amount of friction between the mating surfaces of the flared glass mouthpiece and the silicone gasket. This friction allows the glass to have a greater amount of purchase, or “bite” onto the gasket. With the gasket in place, the material to be vaporized can be loaded into the glass mouthpiece, against its screen, and the mouthpiece can be temporarily attached to the vaporization unit. The glass mouthpiece will stay attached to the vaporization unit until it is removed by the user.

Variations or modifications to the subject matter of this vaporizer may occur to those skilled in the art upon review of the invention as described herein. Such variations, if within the spirit of this invention, are intended to be encompassed within the scope of any claims to patent protection issuing upon this development. The description of the invention in the preferred embodiment, and its depiction in the drawings, are generally set forth for illustrative purposes only. 

I claim:
 1. A vaporizer device provided to extract the active compounds from a sample of plant material, said device including a mouthpiece, a heat exchanger, the heat exchanger capable of being coupled with the mouthpiece, the heat exchanger having a surface area capable of exposure to significantly heated air and flame to provide for substantially heating the air passing through the heat exchanger during inhalation by the user of said device, a burner, said burner formed as a torch-style butane lighter, capable of ignition of its fuel during usage, said burner locating within a housing, a chimney provided upon the butane lighter and its housing, said chimney provided for holding the heat exchanger substantially diametrically centered therethrough, such that when the butane lighter is ignited, its generated flame and heated air pass by the heat exchanger, heating the air inhaled through it or passing the heated air through the mouthpiece and vaporizing the active compounds of the plant material contained within the mouthpiece, during usage of the vaporizer device.
 2. The vaporizer device of claim 1, and including a heat shield provided upon the chimney, and capable of surrounding substantially the heat exchanger as to shelter the user from the heat generated by the lighter during operations of the device.
 3. The vaporizer device of claim 1, wherein said chimney includes a lower chimney that is arranged above the butane lighter, and an upper chimney that couples onto the top of the lower chimney, and embraces the location of the heat exchanger therethrough during its installation.
 4. The vaporizer device of claim 1, wherein said heat exchanger includes a flattened surface, to provide greater exposure of the heat exchanger to the generated flame and heated air, and to enhance the heating of the air inhaled through the heat exchanger and the mouthpiece during usage of the vaporizer device.
 5. The vaporizer device of claim 4, wherein said body housing formed of two parts, the two parts capable of being fastened together to furnish an insulated housing around the location of the butane lighter to shield the user from the generated heat.
 6. The vaporizer device of claim 1, wherein said mouthpiece having a flared end, and the proximate end of the heat exchanger capable of inserting within said mouthpiece flared end during usage.
 7. The vaporizer device of claim 6, wherein said flared end of the mouthpiece device forming a vaporization chamber into which plant material may locate when located into position for exposure to the substantially heated air inhaled therethrough to provide for extraction of the plant material active compounds during usage of the vaporization device.
 8. The vaporization device of claim 7, wherein said flared end of the mouthpiece device is removable, and a filter locates therein to prevent the inhalation of plant material into the users mouth during usage of the device.
 9. The vaporization device of claim 8, wherein said filter comprises a screen.
 10. The vaporization device of claim 3, wherein said upper chimney includes a screen to prevent any extraneous debris from entering into the chimney to prevent clogging of the flame exhaust path.
 11. The vaporization device of claim 10, wherein said lower chimney locates said heat exchanger within the vaporization device, and thereby providing a semicircular exhaust path to either side of the heat exchanger as the lighter flame passes there past on its way to exhausting from the top of the heat shield.
 12. The vaporization device of claim 1, wherein said vaporization device includes a torch-style butane lighter, a piezoelectric igniter which when actuated provides for ignition of the butane discharging from the lighter, a button means operatively associated with said lighter, to provide for its initiation, an insulator coupled to the butane lighter to provide for controlled passage of its butane gas therethrough during actuation, said insulator provided for mounting the upper end of the lighter, and an adjustment valve operatively associated with the butane lighter to regulate the amount of fuel being discharged from the lighter through the insulator for passage into the chimney and ignited for heating of the heat exchanger of the vaporization device during its usage.
 13. A vaporizer device provided to extract the active compounds from a sample of plant material, said device including at least a mouthpiece and a heat exchanger, said heat exchanger capable of being coupled with the mouthpiece, the heat exchanger having a surface area capable of exposure to significantly heated air and flame to provide for substantially heating the air passing through the heat exchanger during inhalation by the user of said device, such that during operations of the device the plant material is located within the mouthpiece, spacidly from the heat exchanger, in order to convectively heat the plant material during application and usage of the vaporizer device.
 14. The vaporizer device of claim 13, wherein such heat exchanger includes a flattened surface to provide greater exposure of the heat exchanger with a heat generated by the device, and to enhance the heating of the air inhaled through the heat exchanger and the mouthpiece during usage of the vaporizer device.
 15. The vaporizer device of claim 14, wherein said mouthpiece having a flared end, and the approximate end of the heat exchanger capable of inserting within said mouthpiece flared and during usage.
 16. The vaporizer device of claim 15, wherein said flared end of the mouthpiece device is removable, and a filter locates therein to prevent the inhalation of any plant material into the user's mouth during usage of the device.
 17. The vaporization device of claim 16 and including a gasket, capable of application upon an end of the heat exchanger, a clamp provided upon the heat exchanger to limit the extent of application of the gasket onto said heat exchanger, and said mouthpiece capable of application onto the gasket when assembling the mouthpiece to the heat exchanger in preparation for usage of the vaporization device.
 18. The vaporization device of claim 1, wherein the device assembles for single handed usage. 